This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to transplantation of the nucleus pulposis in conjunction with such treatment.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of each disc is the nucleus pulposus which, in the adult human, is composed of cells and an insoluble extracellular matrix which is produced by the nucleus itself. The extracellular matrix is composed of collagen, proteoglycans, water, and noncollagenous proteins. The nucleus pulposus is surrounded by the annulus fibrosis, which is composed of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus.
The cells of the nucleus pulposus have chondrocyte-like features. In an adult human, the cells of the nucleus pulposis obtain nutrients and eliminate waste by diffusion through blood vessels in the endplates of the vertebrae adjacent to the disc. Blood vessels do not course into the nucleus pulposis. The relative vascular isolation of the nucleus pulposis imparts isolation of nucleus pulposis cells from the body""s immune system.
To date, the treatment of degenerative disc disease has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, most prior-art techniques use synthetic materials to replace the entire disc or a portion thereof. My pending U.S. patent application Ser. No. 09/415,382 discloses disc replacement methods and apparatus using synthetic materials.
Unfortunately, disc replacement using synthetic materials does not restore normal disc shape, physiology, or mechanical properties. Synthetic disc replacements tend to wear out, resulting in premature failure. The problems associated with the wear of prosthetic hip and knees are well known to those skilled in orthopedic surgery. The future of treating degenerative disc disease therefore lies in treatments which preserve disc function. If disc function could be restored with biologic replacement or augmentation, the risk of premature wearout would be minimized, if not eliminated.
My U.S. patent application Ser. No. 09/639,309, filed Aug. 14, 2000, is directed to a method of treating a diseased or traumatized intervertebral disc through the transplantation of nucleus pulposis cells. Broadly according to the method, live nucleus pulposus cells are harvested from a human or animal donor and introduced into the disc being treated. The harvested nucleus pulposus cells are preferably kept viable until placed into the disc being treated.
A preferred embodiment includes morselizing the harvested nucleus pulposus cells and extracellular matrix, forming a passageway through the annulus fibrosis, and transplanting the harvested nucleus pulposus cells and extracellular matrix into the disc through the passageway. For example, the harvested nucleus pulposus cells and extracellular matrix may be introduced into the disc using a needle and syringe or small cannula.
One or more therapeutic substances may be added to the harvested nucleus pulposus cells and extracellular matrix including culture media, growth factors, differentiation factors, hydrogels, polymers, antibiotics, anti-inflammatory medications, or immunosuppressive medications. Alternatively the step of transplanting the harvested nucleus pulposus cells and extracellular matrix may include percutaneously or laparoscopically injecting the engineered disc tissue into the disc being treated.
The relative vascular isolation of the nucleus pulposis imparts isolation of nucleus pulposis cells from the body""s immune system. However, even with the lack of an immune system response, the transplantation risks viral disease transmission, i.e. hepatitis, HIV etc. The risk of disease transmission increases in direct proportion to the number donors who provide disc tissue.
Broadly, this invention resides in tissue banking to guard against the spread of transmittable diseases. Although the description makes specific reference to human disc cells, the invention may be used as a way to provide disease-free disc tissue derived from animal sources, and is applicable as well to other types of biologic tissues and materials such pancreas cells, cartilage cells, and so forth.